Grinding disc



FIG. 1 is a perspective view of a grinding disc showing my new design;

FIG. 2 is a side elevational view thereof;

FIG. 3 is an end elevational view taken from the right of FIG. 2;

FIG. 4 is an end elevational view taken from the left of FIG. 2.

The ornamental design for a grinding disc, as shown. 